The present invention relates to polyurethane-backed articles. The present invention particularly relates to polyurethane-backed articles and to a process and composition used in making same.
Articles having attached polyurethane foam layers are well known. For example, carpets and other substrates having attached polyurethane foam layers as backing are described in U.S. Pat. Nos.: 3,755,212; 3,821,130; 3,862,879; 4,022,941; 4,171,395; 4,278,482; 4,286,003; 4,296,159; 4,405,393; 4,483,894; 4,512,831; 4,515,646; 4,595,436; 4,611,044; 4,657,790; 4,696,849; 4,853,054; 4,853,280 and, 5,104,693. Typically a filler material is used to prepare a polyurethane formulation for carpet backing. The filler can replace some of the polymer required to prepare a polyurethane backed article, while maintaining bulk in the article. This can lower the cost of production of the article, since materials used as fillers are typically less expensive than the polymer material that is being replaced.
In selecting a filler for a particular application, the effect that the filler can have on the processxe2x80x94and on the physical properties of the articlexe2x80x94should be considered. For example, in a process for preparing polyurethane backed carpets, a filler that is too alkaline can cause premature gellation. Conversely, a filler that is too acidic can cause an unacceptable delay in the onset of gellation. Increasing the amount of conventional fillers used in preparing carpet backing, such as calcium carbonate (CaCO3) and aluminum trihydrate (ATH), can result in an undesirable viscosity increase in a polyurethane formulation.
While cost reduction can be an incentive for introducing as much filler as possible into a polyurethane formulation, it can be unacceptable to reduce the cost of production at the expense of the quality of the article produced. The amount of filler incorporated into a polyurethane formulation can be limited by the adverse effects that the filler can have on the properties of a polyurethane, such as flexibility, resiliency, and adhesion, for example.
Fly ash has been used as a filler material in systems such as cement and concrete products, roadbases/subbases, and structural fills. See, for example, U.S. Department of Transportation/Federal Highway Administration Report No. FHWA-SA-94-081 (August 1995). The Electric Power Research Institute (EPRI), in EPRI Report CS-4765 (September 1986) (hereinafter CS-4765), reported that fly ash recovered from a direct acid leaching process was added as a filler to polymerized nylon and polypropylene.
It would be desirable to increase the loading of filler into a polyurethane formulation without detriment to the process of preparing a polyurethane carpet backing, or to the final physical properties of the final product. It would also be desirable to use fly ash as a filler material in a reactive polymeric system without significant effect on a polymer forming reaction.
In one aspect, the present invention is a polyurethane-forming composition, useful for preparing a polyurethane precoat, polyurethane laminate coat, or polyurethane foam coat comprising a polyol; a chain extender; a polyisocyanate; a catalyst; a surfactant; a filler wetting agent; and a filler, wherein the filler includes fly ash; and optionally including a surfactant and a blowing agent.
In another aspect, the present invention is a backed carpet having a polyurethane backing that includes at least one coat of polyurethane that is prepared from a polyurethane-forming composition comprising a polyol; a chain extender; a polyisocyanate; a catalyst; a filler wetting agent; a filler, wherein the filler includes fly ash; and optionally including a surfactant and a blowing agent.
In still another aspect, the present invention is a process for preparing a carpet having a polyurethane backing comprising the steps: (1) applying at least one layer of a polyurethane-forming composition to a carpet substrate, wherein the polyurethane-forming composition includes fly ash; and (2) curing the polyurethane-forming composition to form a tack-free polyurethane backing. Applicant has developed a process for preparing a polyurethane composition which incorporates fly ash as a filler material. The process of the present invention can result in an improved process, including increased flow of a polyurethane composition into the backstitch of a carpet, and increased pot life of a polyurethane composition. The use of fly ash as filler reduces pilling and fuzzing of the carpet face, improves flexibility of the carpet during installation, and also reduces puddle gellation during application of a polyurethane-forming composition. In addition, fly ash can be included at a higher loading than conventional fillers, without detriment to established process parameters or to the physical properties of a polyurethane carpet backing.
The polyurethane-forming composition of the present invention comprises a polyol as described herein, a chain extender, a polyisocyanate, a catalyst as described herein, a surfactant, a filler wetting agent, and a filler that includes fly ash. The composition of the present invention contains reactive components such as active hydrogen containing compounds and compounds having isocyanate functionality.
Active hydrogen containing compounds are compounds having active hydrogen functionality, wherein at least one hydrogen atom is bonded to an electronegative atom such as sulfur, nitrogen, or oxygen. Active hydrogen containing compounds described herein can contain any combination of hydroxyl , amino, and mercaptyl functionalityxe2x80x94in addition to other active hydrogen groupsxe2x80x94and can be reacted with isocyanate groups under conditions suitable for preparing a polyurethane carpet backing. The average functionality of an active hydrogen containing compound refers to the average number of active hydrogen groups per compound.
A polyol is an example of an active hydrogen containing compound, in the present invention. As used herein, the term xe2x80x9cpolyolxe2x80x9d can refer to a single polyol or to a mixture of two or more polyols. A polyol of the present invention can have an average equivalent weight of from about 500 to about 5000, preferably from about 750 to about 2500, and more preferably from about 750 to about 2000. The average equivalent weight of a compound can be determined by dividing the average molecular weight of the compound by the functionality of the compound. In the present invention, at least about 30 percent, preferably about 50 percent, and more preferably about 60 percent of the hydroxyl functionality of a polyol is primary hydroxyl functionality. While a wide range of materials can be used, polyether polyols are preferred based on their performance and wide availability. Polymers of propylene oxide which are at least partially end-capped with ethylene oxide are particularly preferred.
Polyols of the present invention are prepared by known methods by reacting an alkylene oxide with a suitable polyhydric initiator compound. The alkylene oxide preferably has 2-8 carbon atoms. For example suitable alkylene oxides can be ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, styrene oxide, epichlorohydrin, 3-methyl-1,2-butylene oxide, like compounds and mixtures thereof, with propylene oxide being the preferred oxide. The initiator compound can be a polyhydric compound such as water, ethylene glycol, propylene glycol, 1,2-butane diol, 1,3-butane diol, glycerine, trimethylol propane, p,pxe2x80x2-isopropylidine diphenol, aniline, ammonia, ethylene diamine, aminoethylethanolamine, like compounds and mixtures thereof.
When a single polyol is used in the present invention, the polyol can have an average functionality of from about 1.4 to about 3.0. Preferably the average functionality of the polyol is from about 1.6 to about 2.8. A mixture of polyols can be used which includes at least a second polyol in addition to the first polyol. The second polyol can be described in the same manner as the first polyol except that the second polyol can have a functionality of at least about 2.05. Preferably, the second polyol has a functionality of from about 2.4 to about 3.0, more preferably the functionality is from about 2. 5 to about 2.95. When a polyol mixture is used, the average functionality of the polyol mixture can be from about 1.97 to about 2.5, preferably from about 1.98 to about 2.4 and more preferably from about a 1.99 to about 2.3.
The present invention optionally includes a chain extender. A chain extender is typically a low equivalent weight active hydrogen containing compound having about 2 active hydrogen groups per molecule. The active hydrogen groups can be hydroxyl, mercaptyl, or amino groups. If the active hydrogen groups are amino groups then the amine is preferably a sterically hindered amine. A sterically hindered amine is an amine that is substituted with bulky groups that tend to inhibit the reactivity of the amine, for example alkyl groups having 2 or more carbons. An amine chain extender can also be blocked, encapsulated, or otherwise rendered less reactive. Preferred chain extenders include glycols and glycol ethers such as: ethylene glycol; 1,4-butane diol; 1,6-hexamethylene glycol; dipropylene glycol; tripropylene glycol; diethylene glycol; triethylene glycol; cyclohexanedimethanol; the diverse bisphenols; like compounds and mixtures thereof. Suitable amine chain extenders include: methylene bis(o-chloroaniline); NaCl-blocked methylene dianiline; diethyltoluenediamine; like compounds, and mixtures thereof.
In preparing a polyurethane backing of the present invention, small amounts of chain extender are advantageously used. Generally, from about 5 to about 50 parts, preferably from about 5 to about 30 parts of the chain extender per 100 parts of polyol, by weight, are used. More preferably from about 5 to about 20 parts of chain extender per 100 parts of polyol are used in the practice of the present invention.
The polyurethane-forming composition of the present invention also includes a polyisocyanate. The average functionality of a polyisocyanate is the average number of isocyanate groups per molecule. The polyisocyanate used herein has an average functionality of from about 1.9 to about 3.0. The polyisocyanate preferably has an average functionality of about 1.95 to about 2.5, and more preferably from about 1.95 to about 2.4. Most preferably, the polyisocyanate has an average functionality of from about 2.0 to about 2.4.
The polyisocyanate can be aliphatic or aromatic. Aromatic polyisocyanates suitable for use herein include: phenyl diisocyanate; 2,4-toluene diisocyanate; 2,6-toluene diisocyanate; ditoluene diisocyanate; naphthalene 1,4-diisocyanate; 2,4xe2x80x2- and/or 4,4xe2x80x2-diphenylmethane diisocyanate (MDI); polymethylene polyphenylenepolyisocyanates (polymeric MDI); like compounds, and mixtures thereof. Suitable aliphatic polyisocyanates include: the hydrogenated derivatives of suitable aromatic polyisocyanates such as 1,6-hexamethylene diisocyanate; isophorone diisocyanate; 1,4-cyclohexyl diisocyanate; like compounds and mixtures thereof. Prepolymers prepared by reacting a polyol or chain extender with a polyisocyanate are suitable, as well.
The polyisocyanate can be used in an amount suitable to prepare a polyurethane-forming composition with an isocyanate index of from about 85 to about 130. The isocyanate index can be calculated by multiplying the ratio of isocyanate equivalents to active hydrogen equivalents by 100. The preferred isocyanate index is a variable that depends on the amount of water in the textile. Preferably the isocyanate index is in the range of from about 85 to about 115 for a laminate coat, and preferably from about 85 to about 110 for a foam coat.
A catalyst is used in the practice of the present invention. Suitable catalysts include tertiary amines, and organometallic compounds, like compounds and mixtures thereof. For example, suitable catalysts include di-n-butyl tin bis(mercaptoacetic acid isooctyl ester), dimethyltin dilaurate, dibutyltin dilaurate, dibutyltin sulfide, stannous octoate, lead octoate, ferric acetylacetonate, bismuth carboxylates, triethylenediamine, N-methyl morpholine, like compounds and mixtures thereof. An amount of catalyst is advantageously employed such that a relatively rapid cure to a tack-free state is obtained. If an organometallic catalyst is employed, such a cure can be obtained using from about 0.01 to about 0.5 parts per 100 parts of the polyurethane-forming composition, by weight. If a tertiary amine catalyst is employed, the catalyst preferably provides a suitable cure using from about 0.01 to about 3 parts of tertiary amine catalyst per 100 parts of the polyurethane-forming composition, by weight. Both an amine type catalyst and an organometallic catalyst can be employed in combination.
The present invention includes a filler material. The filler material includes fly ash. The filler can be exclusively fly ash, or it can optionally include conventional fillers such as milled glass, calcium carbonate, ATH, talc, bentonite, antimony trioxide, kaolin, or other known fillers. Preferably, fly ash makes up at least 50 percent by total weight of the filler used in the present invention. More preferably, fly ash makes up at least 75 percent of the filler, and even more preferably at least 90 percent of the filler used in the present invention. Most preferably fly ash makes up substantially all of the filler material, i.e. at least 99 percent of the filler is fly ash.
Fly ash is a residue that results from the combustion of pulverized coal, and can include various proportions of oxides of silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), and magnesium (Mg). The major portion of fly ash is composed of oxides of aluminum and silicon. Fly ash can be classified as either Class C or Class F type fly ash. Class C fly ash is obtained from subbituminous and lignite coals. Class F fly ash is obtained from bituminous and anthracite coals. The fly ash of the present invention is Class F fly ash. The fly ash used in the present invention can be treated according to known processes to remove impurities or undesirable components. For example, fly ash can be treated by water washing. Alternatively, fly ash can be treated by direct acid leaching (DAL) as described in CS-4765. As another alternative, fly ash suitable for use with the present invention can be purchased commercially.
Fly ash can be included in a formulation of the present invention at a higher loading than can be obtained using conventional fillers. Fly ash can be loaded at greater than 400 parts of fly ash per 100 parts of active hydrogen compounds. Conventional fillers loaded at greater than 400 parts per 100 parts can cause problems in a process for preparing a polyurethane carpet backing. For example, conventional fillers can cause an unacceptable viscosity increase in a polyurethane-forming formulation when included at a concentration of greater than 400 parts. For the purposes of the present invention, filler can be loaded into a precoat or laminate coat at a concentration of from about 100 to about 1000 parts of filler per 100 parts of active hydrogen containing compounds. Preferably the filler is loaded at a concentration of from about 300 to about 900 parts per 100 parts. More preferably the filler is loaded at a concentration of from about 300 to about 700 parts per 100 parts of active hydrogen containing compounds. In a foam coat, filler can be loaded at a concentration of from about 100 to about 400 parts of filler per 100 parts of active hydrogen containing compounds. Preferably, filler is loaded at from about 150 to 400 parts, more preferably from about 200 to about 400 parts.
The present invention also includes a filler wetting agent. A filler wetting agent generally performs the function of compatiblizing the filler and the polyurethane-forming composition. Useful filler wetting agents can include ethoxylated phosphate esters in an organic carrier. Examples of suitable filler wetting agents include Maphos(trademark) 56, Pegafax(trademark) 410, and Code 5027 (available from Fibro Chem, Inc.). Other useful filler wetting agents could include sodium lauryl sulfate, oleoylsarcosine, cocoamide, and triisopropanolamine stearate.
A filler wetting agent can be included in a polyurethane-forming composition of the present invention at a concentration of at least about 0.5 parts per 100 parts of filler, by weight. Preferably the filler wetting agent is included at a concentration of from about 0.5 to about 1.5 parts per 100 parts of filler, more preferably from about 0.75 to about 1.25 parts per 100 parts of filler.
The present invention can include other optional components. For example, a polyurethane-forming composition of the present invention can include a surfactant, a blowing agent, a flame retardant, pigments, antistatic agents, reinforcing fibers, antioxidants, preservatives, water scavengers, acid scavengers, and the like. Examples of suitable blowing agents include gases such as air carbon dioxide, nitrogen, argon, helium, and the like; liquids such as water, volatile halogenated alkanes such as the various chlorfluoromethanes and chlorfluoroethanes; azo-blowing agents such as azobis(formamide). Preferred in the practice of this invention is the use of a gas as a blowing agent. Particularly preferable is the use of air as a blowing agent.
A surfactant can be desirable in the present invention. A surfactant can be particularly useful in preparing a polyurethane foam coat, or a polyurethane laminate coat using a composition of the present invention. Suitable surfactants include block copolymers of ethylene oxide and silicone surfactants. For example, suitable block copolymers of ethylene oxide include copolymers having at least 60 weight percent of the polymer being derived from oxyethylene units, 15 to 40 weight percent of the polymer being derived from polydimethylsiloxane units, and the polymer having a molecular weight of less than 30,000, as described in U.S. Pat. No. 4,483,894. A surfactant can be included in a formulation of the present invention in an amount ranging from about 0.01 to about 2 parts per 100 parts by weight of polyol.
Backed carpets can include a precoat and a laminate coat applied to the back of a carpet substrate. In addition, a backed carpet can optionally include an attached foam cushion that is applied to the carpet substrate. Generally, carpets having attached cushions are prepared by tufting or weaving yam into a primary backing, applying an adhesive precoat to the primary backing to bind the tufted material into the backing, and then applying a polyurethane foam cushion. Use of any of the polyurethane coats can be optional in the practice of the present invention. For example, application of a separate polyurethane precoat can be eliminated by application of a sufficient amount of a laminate coat, such that the laminate coat soaks into the carpet weave and performs the function of both a precoat and a laminate coat. Similarly, a polyurethane foam coat can be applied in an amount sufficient to eliminate separate application of a polyurethane precoat and/or laminate coat.
Use of a precoat layer is preferred because use of a precoat allows greater flexibility in the processing conditions used in preparing a polyurethane backed carpet. For example, use of a precoat allows use of higher functionality in a polyurethane laminate coat composition. Higher functionality tends to have a detrimental effect on the physical properties of a carpet. A precoat layer can prevent a subsequent laminate coat or foam coat from penetrating the carpet weave, thereby enabling use of a laminate or foam coat having higher functionality without detriment to carpet properties.
In preparing polyurethane-backed carpets according to this invention, the individual components of the polyurethane-forming composition are mixed and applied as a layer of preferably uniform thickness onto one surface of the carpet substrate. It is often preferable to pre-mix all components except the polyisocyanate (and optional blowing agent, when a gas is used) to form a formulated xe2x80x9cB-sidexe2x80x9d. This simplifies the metering and mixing at the time the polyurethane-forming composition is prepared. In preparing a frothed polyurethane backing, it is preferred to mix all components and then blend a gas into the mixture, using equipment such as an Oakes or Firestone roamer.
The polyurethane-forming composition is then applied to one surface of a carpet substrate before it cures to a tack-free state. Typically the polyurethane-forming composition is applied to the surface attached to a primary backing. The composition may be applied to the carpet substrate before any substantial curing occurs, using equipment such as a doctor knife, air knife, or extruder to apply and gauge the layer. Alternatively, the composition may be formed into a layer on a moving belt or other suitable apparatus and partially cured, then married to the carpet substrate using equipment such as a double belt (also known as double band) laminator or a moving belt with an applied foam cushion. The amount of polyurethane-forming composition used can vary widely, from about 5 to about 500 ounces per square yard, depending on the characteristics of the textile. After the layer is applied and gauged, the layer is cured using heat from any suitable heat source such as an infrared oven, a convection oven, or heating plates. A temperature of from 100xc2x0 C. to about 170xc2x0 C., and a time of from about 1 minute to about 60 minutes are suitable for curing the polyurethane.